1. Field
Embodiments of the present invention relate to display systems.
2. Related Art
A variety of display devices/display systems have been developed. Examples thereof include liquid crystal display (LCD) devices and organic light emitting display (OLED) devices. These displays are lighter in weight than, and smaller in volume than, conventional cathode ray tube displays.
OLED displays and local dimming LCDs use a subset of individual emitters (e.g., OLEDs of pixels, or LEDs for driving backlight units of an LCD) to depict imagery in different parts of a panel/display screen of the display system to represent the displayed image. By activating the emitters, light is produced from a panel of the display system. By displaying bright objects having a larger size in the displayed image, the total number of active emitters increases along with a total power demand of the display system. If the total number of emitters becomes too large, due to limitations of the display system, it might not be feasible to power all of the emitters at an intensity at which a small number of active emitters could be powered.
For example, by driving the panel to be entirely white, the aggregate power used by all emitters may be large. That is, because the total power required to drive a relatively small number of active emitters at a particular intensity in a relatively small area of the panel is less than the power required to drive a larger number of active emitters in a larger area at the same intensity, the display system may not be engineered to be able to suitably supply the power load used to drive the large number of active emitters at that intensity.
Accordingly, display systems may incorporate a form of net power control (NPC) that decreases a global gain/NPC gain of all emitters as the total system load gets larger as a function of a number of the emitters, and as a function of respective intensities at which the emitters display light. That is, the overall brightness of the image may be dimmed as the number of active emitters operating at a relatively high intensity increases, thereby reducing the intensity of all of the active emitters, and thereby reducing the power draw for powering the active emitters and consequently reducing the image brightness as seen by an observer. The value/level of the global gain applied to the image is determined by a NPC function/algorithm, and corresponds to the loading of the panel (e.g., a panel load, or the amount of power used to drive the panel, which generally corresponds to the brightness of the panel). That is, the NPC function/NPC control signal may determine the global gain as a function of the total emitter load. By reducing the total system load by using a global gain function, the circuitry of the display system may be protected by preventing overload of a power supply of the display system that drives the emitters, preventing overload of power lines from the power supply to the emitters, or preventing excessive heat buildup.
A power control signal for driving the display panel is controlled by the NPC function, and is typically based on a power load estimate corresponding to the pixel data of each image frame of image data. In sequences of the image data that correspond to a change in the panel loading (e.g., a sudden change in the panel loading), the NPC function may decrease the global gain and thereby dim the active emitters (e.g., when the size of a relatively bright area on the panel increases, the brightness of that bright area may decrease). A user viewing the panel may detect a change (e.g. sudden change) in the image intensity corresponding to the change of the global gain. In some cases, the NPC function, which has generally been a static function for conventional display systems, can cause a 60% reduction or more in the brightness of the panel.
The above information disclosed in this Background section is only to enhance the understanding of the background of the invention, and therefore it may contain information that does not constitute prior art.